The present invention relates to an ultrasonic driving motor comprising a rotor having slide projections in contact with an edge face of a piezoelectric vibrator.
The applicant presented a ultrasonic driving motor comprising a piezoelectric vibrator having electrodes divided in two on each side of the vibrator the positions of electrodes on the both sides of the vibrator are shifted slightly in relation to the electrodes on the other side, and when AC power is applied to set of electrodes on both sides of the piezoelectric vibrator, a progressive wave is generated on the edge face and both sides of the piezoelectric vibrator (see U.S. Pat. No. 4,945,275 and Japanese laid open Application Sho No. 64-30477).
However, in the ultrsasonic driving motor, because the rotor is in contact with the electrodes on the piezoelectric vibrator by the pressure of a spring, the electrodes are worn in a short time by the rotor. Also, if the electrodes are protected from wear by mounting a cover on the electrodes, the rotor is worn by rotation thereof, the pressure between the piezoelectric vibrator and the rotor is changed and the ultrasonic driving motor does not have a long life.